In a well known prior art package winding apparatus, a strand guide, of the type sometimes referred to as a guide eye, is reciprocated by a traversing mechanism parallel to the axis of rotation of a winding mandrel. Strand material is guided by the guide onto the rotating winding mandrel so as to be helically wound into a package build on the mandrel.
The traversing mechanism comprises a cam having an endless helical cam groove and rotated about an axis parallel to that of the winding mandrel, and the guide member is secured to a cam follower engaging in the cam groove.
The cam is provided within a cylindrical housing extending from the lower end of a cam arm, which is pivotal in a cam arm pivot having an axis of pivotation parallel to the axes of the cam and the winding mandrel.
During the winding of the package, the diameter of the package build on the winding mandrel is sensed and the cam arm, and therewith the cam and the guide member, are pivoted in a stepped movement about the cam arm pivot axis.
Also, the speed of rotation of the winding mandrel is progressively reduced, during the winding of the package, so that the length of strand material drawn into the package build per unit of time, sometimes referred to as the yield, is maintained constant.
The rotational driving of the winding mandrel is effected through a drive transmission from a drive motor, and a cam drive transmission is provided between the winding mandrel drive transmission and the cam so that the cam is rotated in timed relation to the rotation of the winding mandrel.
As the winding of the package proceeds, and consequently the speed of rotation of the winding mandrel is reduced and the speed of rotation of the cam, and thus the speed of reciprocation of the guide member, are correspondingly reduced, the helix angle, i.e. the angle between the strand material wrap on the package build and a plane perpendicular to the winding mandrel axis, is progressively reduced.
This reduction of the helix angle occurs because the cam is rotated in timed relation to the reducing speed of rotation of the winding mandrel in order to maintain a constant waywind ratio, i.e. a constant number of strand wraps on the package build during each traverse of the guide member, and consequently the increasing diameter of the package build results in the strand wrap being deposited at a slightly but increasingly reduced helix angle.
Such reduction of the helix angle has various disadvantages.
For example, when the winding apparatus is employed for winding multistrand packages, for the production of multiple split slivers, the alteration of the helix angle adversely and progressively affects the spacing of the individual strands in the build.
Further, the reduction of the helix angle during the package formation limits the winding speed at which square edge packages can be produced and consequently prevents the winding of stable package builds at high speeds.
In both cases, the winding mandrel speed of rotation is limited both by the maximum speed at which the cam can reciprocate the guide member or guide eye without failure of its component parts and also by the necessity for maintaining a minimum helix angle to ensure stable package builds and/or, in the case of multistrand winding, adequate spacing of the strands in the package build.